linux-kernel - [RFC 15/33] KVM: x86/mmu: Introduce infrastructure to handle non-executable faults

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Message-ID: <20231108111806.92604-16-nsaenz@amazon.com>
Date:   Wed, 8 Nov 2023 11:17:48 +0000
From:   Nicolas Saenz Julienne <nsaenz@...zon.com>
To:     <kvm@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-hyperv@...r.kernel.org>,
        <pbonzini@...hat.com>, <seanjc@...gle.com>, <vkuznets@...hat.com>,
        <anelkz@...zon.com>, <graf@...zon.com>, <dwmw@...zon.co.uk>,
        <jgowans@...zon.com>, <corbert@....net>, <kys@...rosoft.com>,
        <haiyangz@...rosoft.com>, <decui@...rosoft.com>, <x86@...nel.org>,
        <linux-doc@...r.kernel.org>,
        Nicolas Saenz Julienne <nsaenz@...zon.com>
Subject: [RFC 15/33] KVM: x86/mmu: Introduce infrastructure to handle non-executable faults

The upcoming per-VTL memory protections support needs to fault in
non-executable memory. Introduce a new attribute in struct
kvm_page_fault, map_executable, to control whether the gfn range should
be mapped as executable.

No functional change intended.

Signed-off-by: Nicolas Saenz Julienne <nsaenz@...zon.com>
---
 arch/x86/kvm/mmu/mmu.c          | 6 +++++-
 arch/x86/kvm/mmu/mmu_internal.h | 2 ++
 arch/x86/kvm/mmu/tdp_mmu.c      | 8 ++++++--
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 2afef86863fb..4e02d506cc25 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3245,6 +3245,7 @@ static int direct_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 	struct kvm_mmu_page *sp;
 	int ret;
 	gfn_t base_gfn = fault->gfn;
+	unsigned access = ACC_ALL;
 
 	kvm_mmu_hugepage_adjust(vcpu, fault);
 
@@ -3274,7 +3275,10 @@ static int direct_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 	if (WARN_ON_ONCE(it.level != fault->goal_level))
 		return -EFAULT;
 
-	ret = mmu_set_spte(vcpu, fault->slot, it.sptep, ACC_ALL,
+	if (!fault->map_executable)
+		access &= ~ACC_EXEC_MASK;
+
+	ret = mmu_set_spte(vcpu, fault->slot, it.sptep, access,
 			   base_gfn, fault->pfn, fault);
 	if (ret == RET_PF_SPURIOUS)
 		return ret;
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index b66a7d47e0e4..bd62c4d5d5f1 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -239,6 +239,7 @@ struct kvm_page_fault {
 	kvm_pfn_t pfn;
 	hva_t hva;
 	bool map_writable;
+	bool map_executable;
 
 	/*
 	 * Indicates the guest is trying to write a gfn that contains one or
@@ -298,6 +299,7 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 		.req_level = PG_LEVEL_4K,
 		.goal_level = PG_LEVEL_4K,
 		.is_private = kvm_mem_is_private(vcpu->kvm, cr2_or_gpa >> PAGE_SHIFT),
+		.map_executable = true,
 	};
 	int r;
 
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 6cd4dd631a2f..46f3e72ab770 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -957,14 +957,18 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu,
 	u64 new_spte;
 	int ret = RET_PF_FIXED;
 	bool wrprot = false;
+	unsigned access = ACC_ALL;
 
 	if (WARN_ON_ONCE(sp->role.level != fault->goal_level))
 		return RET_PF_RETRY;
 
+	if (!fault->map_executable)
+		access &= ~ACC_EXEC_MASK;
+
 	if (unlikely(!fault->slot))
-		new_spte = make_mmio_spte(vcpu, iter->gfn, ACC_ALL);
+		new_spte = make_mmio_spte(vcpu, iter->gfn, access);
 	else
-		wrprot = make_spte(vcpu, sp, fault->slot, ACC_ALL, iter->gfn,
+		wrprot = make_spte(vcpu, sp, fault->slot, access, iter->gfn,
 					 fault->pfn, iter->old_spte, fault->prefetch, true,
 					 fault->map_writable, &new_spte);
 
-- 
2.40.1